[uzurpator]

You might be able to use a front derailleur as your chain guide, ironically. Just no shifter/cable. Adjust limit screws as needed. You might need a small bit of cable and an adjuster in some cases.

If he went through all the trouble needed to get an FD to a DH bike, then getting a shifter somewhere on the bars is the least of his problems.

The rear derailleur you have on a DH bike likely can't take up that much extra chain slack.

you can run SS rear mech on a 2x if the chain is sized for the big chainring. Then on the granny you are limited to largest four or so cogs of the cassette. I ran my enduro bikes like this for years.

 

[dudebro]

What sort of a bike is that? Because what you are suggesting is very much possible, but with a series of asterisks, which may cause a lot of headaches.

Firstly, is your crank actually capable of running a small ring? There was 810 crank with bosses for a small ring and - I presume - 83mm BB shell, but it was a niche item. If it has those, then your first problem may be chainguide - small ring interference. On an 83mm and ISCG being a very loose standard, you may simply need to choose a small ring or a chainguide.

If there is space for the small ring, then you'll run into an issue of no top cage for the chain device. There are chain devices for 2x systems, but all of them assume you are running an FD. DH bikes that could mount one are few, and most of them are from mid-2000s - like Spesh demo 9.

You can run a dh bike without a chain device but it would require having a short-caged clutched rear mech and having at least an outer bash guard to do at least some protection against chain drops.

what sort of drivetrain do you have at this moment?

Short caged DH derailleurs ( Saint, Zee FR, XO ) usually allow to run at least 11-32 cassette; depending on chain growth and chainstay length. Depending on what chainring you run, it may be possible to ride this uphill.

Since this is a DH bike - is it one with a regular cassette or one of those fancy 7 speed mini cluster types?

EDIT:


You may try to run dual N/W rings on the front with a burly bash guard, provided all the necessary mountings are in place. Easiest way to check if this would work is to get some chinese stuff and ride without a chainguide, but with one-sided chain device.

Thanks! Seems like you're the first one who gets my idea. I do not want to add a front derailleur and I do not want to ditch a chain guide. I just wanted to know if someone had ever done something similar to my idea, as there might be clearance issues with dual chainrings and a ISCG chain guide. And I also wanted to know if anyone has a lead of a chain guide where you can open the upper part without tools and then have room to move the chain to the smaller ring. I don't want to add a large cassette or get a long cage RD.

I do have 815 crankset (83 BB) with dual ring possibility, 104 and 64 BCD, do 64 bcd NW rings exist?

 

[dudebro]

You'd better off getting some 1x10 with 11-42 cassette

Why? Saint RD can't handle that. I'd have to change the chain, derailleur and the cassette. If I were to replace all that, why not go all the way and get a truly wide range 12 speed while I'm at it?

To be clear, this is not what I want to do. I know that would be the easiest and most obvious way, but I want to keep short cage derailleur and I do not wish to add unsprung weight with a huge cassette.

 

[uzurpator]

I do have 815 crankset (83 BB) with dual ring possibility, 104 and 64 BCD, do 64 bcd NW rings exist?

Before you start buying parts, go to your favorite bike shop and dive into the dumpster to get any 64mm ring and try to install it with the chain device plate.

Regardless - I'm not aware of any tool-free unmountable chain device. It's kind of their point to keep the chain in Also - for the small ring, the fitment is going to be so tight that it being N/W is not really necessary, there will be no place to fall to.

 

[Bicycle Rider]

Can’t believe all the naysayers—- of course it’s possible to make this work.

personally I’d try it without the guide and see if your clutch and NW ring are enough - but if you definitely need something, there’s this top guide that may be made to work:

Reverse Flip Guide Chain Guide

- Steel chain guide prevents chain drop on 1x drivetrains - Guide cage folds upward for fast crank removal, snaps back into place when done- Micro adjustment system for perfect alignment over the chain- Compatible with round and oval chainrings- Installs easily without removing the crank

reverse-components-usa.com

 

[bpw]

Bring back the HammerSchmidt!

 

[tehllama]

The lazy answer I settled on for this a while back was to get a cheap 2x crankset, run the large narrow/wide ring I really wanted to have the big end there, and then just keep the stock 22T granny inside ring. The end answer is a mediocre chainline, and that manually shifting isn't something I actually have the energy or willingness to do any more than just grunting along in the tallest e.13 cassette offered gear, then just give up and walk... so I just run stuff 1x and leave it alone.
Lame answer in the end, but I do think I may go this route with a gravel/monstercross setup of all things, so that I can run a 30/42T setup (assuming I can find those stupid cranksets for sail at reasonable prices again)... but I'm weird because I'm always wanting to use the same bike to haul my fat self up aggresseively steep dirt climbs, but also chase down roadies on a dropper post and 150mm fork equipped bike because I want to be ridiculous.